Answer: 26 feet.
Step-by-step explanation:he
The exercise is not written clearly. Assuming that it asks to find the amount of lumber (in feet) John needs for 3 shelves, let "x" represents that amount of lumber in feet.
Based on the data provided, you know that one shelf requires [tex]8\frac{2}{3}[/tex] feet of lumber.
You can convert the Mixed number to Decimal number applying these steps:
1. You must divide the numerator of the fraction by the denominator.
2. You must add the result obtained to the Whole number part.
Then you get:
[tex]8\frac{2}{3}=8+0.6667=8.6667[/tex]
Knowing this, you can set up the following proportion:
[tex]\frac{8.6667}{1}=\frac{x}{3}[/tex]
Finally, you must solve for "x" in order to find its value. This is:
[tex](3)(8.6667)=x\\\\x=26.0[/tex]